At present, in various fields where eccentric vibrating mechanisms are used, for example in the engineering machines, such as hydraulic vibrating pile hammer, percussion drill, vibrating roller, vibrating crusher etc., which need vibration operation, in order to improve working efficiency, different optimum amplitudes need to be selected according to different operating conditions, and in order to avoid the machine from being damaged by resonance generated by a resonance area when the machine starts or shuts down, the eccentric moment is desired to be adjustable.
At present, in the eccentric moment adjusting schemes domestic and abroad, the following several forms are mainly comprised: (1) manual adjustment, wherein the eccentric moment is adjusted through changing the phase or weight of an eccentric block, and the machine must shut down during the adjustment; (2) impact block with two-stage, wherein the angle between a movable eccentric block and a fixed eccentric block is changed through the rotation in forward direction and in reverse direction of a motor, so that the purpose of changing the eccentric moment can be achieved, and the principle of this method is similar to that of the manual adjustment scheme in China, and the structure is simple, but the number of the grades of variable moment is limited, such as Chinese patent publication No. CN101503873, titled with “Eccentric Vibrating Mechanism”; (3) sliding gear, wherein the axial movement of a big helical angle herringbone gear is utilized to relatively rotate two groups of synchronizing gears which are meshed with the herringbone gear, so that the purpose of eccentric moment stepless adjustment can be achieved, and this mechanism can obviously realize stepless frequency adjustment, but has a comparatively complex structure, requires the gears having high synchronizing precision, and has poor reliability, such as Chinese patent publication No. CN101581096, titled with “Eccentric Moment Adjustable Hydraulic Vibrating Pile Hammer”; and (4) adjusting shaft with four-shaft helical splines, wherein two segments of steep-lead helical splines with opposite rotation directions are made on the adjusting shaft, the splines are at both ends respectively provided with a gear, wherein one gear is meshed with a synchronizing gear below, and the other gear is meshed with a synchronizing gear above through an intermediate gear, the adjusting shaft slides along the axial direction, and the lower group of eccentric blocks is relatively rotated with respect to the upper group of eccentric blocks, so that the purpose of stepless frequency adjustment can also be achieved. However, this mechanism is bulky, and requires extraordinary high precision, and has poor controlling performance and high cost.
Therefore, in the existing various moment adjustment modes of vibrating pile hammer domestic and abroad, some of them have poor adjusting ability, and some of them have complex mechanisms, especially in the gear rigid synchronous drive mode. Since the structure is complex, the driving members such as gear are easy to be damaged, with the result that the vibrating mechanism in the stepless moment adjustment type is still hard to be generalized until now.